Process for regenerating catalyst for a hydrocarbon conversion zone

ABSTRACT

In one exemplary embodiment, a unit for regenerating a hydrocarbon conversion catalyst for a hydrocarbon conversion zone can generally include passing the hydrocarbon conversion catalyst through, sequentially, a catalyst-disengaging zone having a first atmosphere, an adsorption zone having a second atmosphere, and a regeneration zone including a combustion zone; introducing an inert gas between the first atmosphere and the second atmosphere; and passing a flue gas from the combustion zone to the adsorption zone.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of and claims the benefitof priority from co-pending U.S. application Ser. No. 11/697,346 filedApr. 6, 2007, which in turn claims the benefit of U.S. ProvisionalApplication No. 60/882,689 filed Dec. 29, 2006, both of which are herebyincorporated by reference in their entirety.

FIELD OF THE INVENTION

The invention generally relates to a unit for regenerating a hydrocarbonconversion catalyst.

BACKGROUND OF THE INVENTION

Numerous hydrocarbon conversion processes can be used to alter thestructure or properties of hydrocarbon streams. Generally, suchprocesses include isomerization from straight chain paraffinic orolefinic hydrocarbons to more highly branched hydrocarbons,dehydrogenation for producing olefinic or aromatic compounds,reformation to produce aromatics and motor fuels, alkylation to producecommodity chemical and motor fuels, transalkylation and others.Typically, such processes use catalysts to promote hydrocarbonconversion reactions. As the catalysts deactivate, it is generallydesirable to regenerate them with a moving bed regeneration system. Suchmoving bed regeneration systems are known and exemplary systems, whichalso disclose the removal of chlorides from a regeneration flue gasstream, are disclosed in U.S. Pat. Nos. 5,837,636 (Sechrist et al.) and6,034,018 (Sechrist et al.). Generally, the gas for combustion isrecycled with a portion purged as a flue gas stream. Typically, theseregeneration systems remove halogen-containing material, such aschlorides, from the combustion zone flue gas stream. Usually, the fluegas is passed through a cooler prior to being sent through a vessel,such as a disengaging hopper, that contains spent catalyst, whichadsorbs chlorides from the flue gas. Subsequently, the flue gas can bedischarged to the atmosphere and the spent catalyst may pass to theregeneration zone.

However, it is desirable to prevent gas entrained with the spentcatalyst from the reaction zone from mixing with gas from theregeneration vessel. Particularly, the gas entrained with the catalystcan contain hydrogen and hydrocarbons and the gas from the regenerationzone can contain oxygen along with nitrogen, carbon dioxide, water, andchlorides. Sometimes, a flue gas cannot be passed through thecatalyst-disengaging hopper without risking gas associated with thespent catalyst being forced through the catalyst transfer lines. As aresult, the gas associated with the spent catalyst that can containhydrogen may be forced into the combustion zone of the regenerationvessel. The presence of such a gas in the high temperature and oxygenenvironment of the combustion zone would be highly undesirable and couldlead to an uncontrolled combustion in the regeneration vessel.Alternatively, it is also desirable to prevent gas from the combustionzone from mixing with gas from the catalyst-disengaging hopper, andpossibly the hydrocarbon conversion zone.

Therefore, it would be beneficial to provide a mechanism to removehalogen-containing material, such as chlorides, from the flue gas from aregeneration vessel used in conjunction with a hydrocarbon conversionunit, and generally at the same time separate gases associated with thespent catalyst from reaction gases associated with the regenerationvessel.

BRIEF SUMMARY OF THE INVENTION

In one exemplary embodiment, a process for regenerating a hydrocarbonconversion catalyst for a hydrocarbon conversion zone can generallyinclude passing the hydrocarbon conversion catalyst through,sequentially, a catalyst-disengaging zone having a first atmosphere, anadsorption zone having a second atmosphere, and a regeneration zoneincluding a combustion zone; introducing an inert gas between the firstatmosphere and the second atmosphere; and passing a flue gas from thecombustion zone to the adsorption zone.

Another exemplary embodiment can include a regeneration unit for ahydrocarbon conversion catalyst for a hydrocarbon conversion zone. Theregeneration unit can include a catalyst-disengaging hopper having anupper portion and a lower portion receiving spent catalyst from thehydrocarbon conversion zone, an adsorption vessel communicating with thecatalyst-disengaging hopper where an inert gas may be provided at leastbetween the upper portion of the catalyst-disengaging hopper and theadsorption vessel, and a regeneration vessel including a combustion zonewhere a conduit may extend into the regeneration vessel and communicatethe combustion zone with the adsorption vessel for passing a flue gas tothe adsorption vessel.

A further exemplary embodiment can include a process for regenerating acatalyst for a hydrocarbon conversion zone. The process may includepassing the catalyst through the hydrocarbon conversion zone, andsubsequently, passing the catalyst through a regeneration unit. Theregeneration unit can include a catalyst-disengaging zone containing anintroduced buffer having an inert gas, an adsorption zone communicatingwith the catalyst-disengaging zone via a line wherein the line mayreceive spent catalyst from the catalyst-disengaging zone, and aregeneration zone.

Thus, the embodiments disclosed herein generally allow the adsorption ofchloride compounds from a combustion flue gas by utilizing the spentcatalyst from a hydrocarbon conversion zone. Particularly, theembodiments disclosed herein can provide an inert gas bubble or buffer,such as nitrogen bubble or buffer, between the hydrocarbon conversionzone gas, which often contains hydrogen, and the combustion zone gas,which often contains oxygen, of the regeneration vessel. Moreover, theembodiments disclosed herein can be added to an existing unit to lowerthe halogen-containing material in gas released to the atmosphere.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic process flow diagram showing an exemplaryembodiment disclosed herein.

DEFINITIONS

As used herein, the term “zone” can refer to an area including one ormore equipment items and/or one or more sub-zones. Additionally, anequipment item, such as a reactor or vessel, can further include one ormore zones or sub-zones.

As used herein, the term “adsorption” can refer to the retention of amaterial in a bed containing an adsorbent by any chemical or physicalinteraction between a material, such as a halogen-containing material,in the bed, and includes, but is not limited to, adsorption, and/orabsorption. The removal of the material from an adsorbent, is referredto herein as “desorption.”

As used herein, the term “halogen-containing material” can include ahalogen molecule, such as chlorine or fluorine, or a compound containingone or more independent halogen radicals. Examples of ahalogen-containing material can include chlorine, fluorine, and hydrogenchloride.

As used herein, the term “buffer” or “bubble” generally refers to aninert gas, such as nitrogen, introduced into a region to create a volumeof slightly higher pressure to prevent the intermingling of gases fromrespective first and second atmospheres.

DETAILED DESCRIPTION OF THE INVENTION

Before referencing the drawing FIGURE, a process for regenerating ahydrocarbon conversion catalyst can include a reforming reaction zone, acatalyst regeneration zone, and lines and equipment communicating withthese zones as disclosed in e.g., U.S. Pat. No. 6,034,018 (Sechrist etal.), which is hereby incorporated by reference in its entirety. So,these zones are described schematically in the context of the presentembodiments.

Also as discussed hereinafter in reference to the drawing figures, morethan one embodiment is depicted in a refinery or a petrochemicalproduction facility to conserve drawing figures. However, it should beunderstood that a refinery or a petrochemical production facility caninclude only one of these embodiments, or can include two or more incombination.

The systems and processes disclosed herein can be applicable to a widerange of catalytic hydrocarbon conversion processes including aromaticisomerization, paraffin or olefin isomerization, paraffindehydrogenation, alkylation, and the regeneration of the catalyst.Hydrocarbon conversion processes may include reforming, alkylating,dealkylating, hydrogenating, hydrotreating, dehydrogenating,isomerizing, dehydroisomerizing, dehydrocyclizing, cracking, orhydrocracking. The exemplary embodiment depicted herein can be areforming process.

Flue gas streams from regeneration units of such processes typicallycontain a halogen-containing material such as halides, particularlychlorides, which can require removal if the streams are discharged tothe atmosphere.

Generally, these hydrocarbon processes utilize catalyst, which typicallycontain a metal, such as a noble Group VIII metal, and a halogen, suchas chlorine or fluorine. However, catalytic reforming can be a widelypracticed hydrocarbon conversion process that uses catalystregeneration. Reforming catalysts typically contain chlorine. Anexemplary catalytic reforming process is described in U.S. Pat. No.5,837,636 (Sechrist et al.). The catalyst, which is often in particulateform, may include an alumina, such as an activated alumina, a silicaalumina, a molecular sieve, or an alumina-silicate clay. Analumina-silicate clay may include a kaolin, an attapulgite, a sepiolite,a polygarskite, a bentonite, or a montmorillonite, particularly when theclays have not been washed by acid to remove substantial quantities ofalumina. Such catalysts are disclosed in U.S. Pat. No. 6,034,018(Sechrist et al.).

Referring to FIG. 1, a refinery or a petrochemical production facility100 can include a hydrocarbon conversion unit 200 and a regenerationunit 300. The hydrocarbon conversion unit 200 may include at least onehydrocarbon conversion zone 210, which can include a plurality ofreaction zones or sub-zones housed in one or more reactors. Typically,the conversion zones are arranged in a stacked reactor arrangement or inside-by-side reactors. Moving bed reactors are known to those of skillin the art and exemplary moving bed reactors are disclosed in U.S. Pat.Nos. 4,119,526 (Peters et al.) and 4,409,095 (Peters). The hydrocarbonconversion zone 210 can be operated at a pressure of about 0-about 6,900kPa(g) (about 0-about 1,000 psig), desirably about 260-about 620 kPa(g)(about 37-about 90 psig). Generally, the hydrocarbon conversion zone 210in this embodiment operates at a pressure above about 340 kPa(g) (about50 psig), such as a pressure of about 280-about 660 kPa(g) (about40-about 95 psig).

The general path of the catalyst to and from the hydrocarbon conversionunit 200 and the regeneration unit 300 is depicted. Particularly, thecatalyst can enter at the top of the hydrocarbon conversion unit 200,pass through the at least one hydrocarbon conversion zone 210, and exitthrough a lift conduit 220. Subsequently, the catalyst may travel in thelift conduit 220 to a catalyst-disengaging zone 310 of the regenerationunit 300. Typically, the catalyst-disengaging zone 310 includes acatalyst-disengaging hopper 320 having an upper portion 324 and a lowerportion 328, and contains more than one atmosphere. Generally, the upperportion 324 has a first atmosphere containing, e.g., hydrogen andhydrocarbons. Another atmosphere present in the catalyst-disengaginghopper 320 can contain an inert gas buffer 380, discussed hereinafter.Afterwards, the catalyst can pass through at least one catalyst transferline 386 to an adsorption zone 400. The adsorption zone 400 may have asecond atmosphere containing, e.g., typically less than about 1% byvolume oxygen, and other gases such as nitrogen, carbon dioxide, water,chlorine and chlorides, such as hydrogen chloride. Next, the catalystcan pass through a line 424 (although multiple lines may be used) and aregeneration zone 420 that may include a regeneration vessel 460. Anysuitable regeneration vessel 460 can be utilized, such as thosedisclosed in U.S. Pat. Nos. 6,034,018 (Sechrist et al.) and 5,824,619(Sechrist et al.). Afterwards, the catalyst can pass through theregeneration vessel 460 and through a lift conduit 222 back to thehydrocarbon conversion zone 200.

Typically one or more gases, such as air and/or nitrogen, is provided tothe regeneration vessel 460 for utilization in the combustion zone 480.The combustion zone 480 generally contains one or more combustion gases.These one or more gases traveling through the at least one of the lines436 and 492 can be referred to as a flue gas, and the one or more gasestraveling through the lines 444, 494, and 498 can be referred to as arecycle combustion gas. Generally, the flue gas and the recyclecombustion gas can include up to about 1%, by volume, oxygen, and othergases that can include nitrogen, carbon dioxide, water, and chlorides,such as hydrogen chloride. Typically, the recycle combustion gas cantravel through the line 444 to a recycle compressor 484, be cooled in anexchanger 486, and then pass through a line 494. As used herein, theterm “compressor” generally means a device for transferring a fluid,especially a gas, and can include a device such as a compressor, ablower, or a fan. Desirably, the exchanger 486, and those describedhereinafter whether heating or cooling, are, respectively, indirect heatexchangers utilizing any suitable medium such as air, water, or steam.In the depicted embodiment, air introduced in a line 534 from thedischarge of a compressor 538 can pass through a line 544 to cool therecycle combustion gas. Subsequently, the cooled recycle combustion gascan pass through a heater 496 and then through a line 498 back into thecombustion zone 480. The cooler 486 and the heater 496 may providecontrol of the temperature, and hence the rate of combustion, in thezone 480. Moreover, the heater 496 can be, independently, any suitableheater, including an electric heater, a furnace or a heat exchanger.

The combustion zone 480 can have a halogen-containing material, such aschlorides, present in a gas that is desirably removed before the gas isdischarged to the atmosphere. Typically, a conduit 434 can extend intothe combustion zone 480 of the regeneration vessel 460 to obtain a fluegas stream having a higher average water content and a lower averageoxygen content as compared to the recycle combustion gas. Alternatively,the conduit 434 can couple the regeneration vessel 460 at the top andnot extend into the vessel 460. Generally, the adsorption vessel 410 andthe regeneration vessel 460 can operate at a pressure ranging generallyfrom about 0-about 6900 kPa(g) (about 0-about 1000 psig), preferablyfrom about 30-about 620 kPa(g) (about 5-about 90 psig), more preferablyfrom about 240-about 410 kPa(g) (about 35-about 60 psig), and optimallyabout 240-about 310 kPa(g) (about 35-about 45 psig). Usually thecombustion zone 480 can be at a pressure of about 243 kPa(g) (about 35.3psig). With the conduit 434 extended into the regeneration vessel 460,the flue gas obtained from the combustion zone 480 aids in minimizingthe water content in the gas recycled in the lines 494 and 498 becausethe flue gas in the conduit 434 has a higher level of water than therecycle gas. Absent withdrawing flue gas from the conduit 434, the watercontent in the recycle gas can stabilize at a higher concentration.Withdrawing the combustion gas from the combustion zone 480 via theconduit 434 can minimize the water content in the recycle gas, which canprolong catalyst life by slowing the degradation in the catalyst surfacearea after repeated regenerations. Consequently, passing the flue gasthrough the conduit 434 in the regeneration vessel 460 can result inlower water content in the recycle gas.

A hood and screen can be provided at an inlet of the conduit 434 toprevent plugging due to catalyst particles. The conduit 434 can beprovided, e.g., as disclosed in U.S. Pat. Nos. 5,001,095 and 5,376,607.The pressure in the regeneration vessel 460 can be at a slightly higherpressure, such as about 243 kPa(g) (about 35.3 psig) than the adsorptionzone 400 at, e.g., about 240 kPa(g) (about 35.0 psig). The flue gas mayescape through the conduit 434 and into a line 436. Afterwards, the fluegas can pass through a valve 438 and be subsequently cooled in anexchanger or cooler 448. Generally, the exchanger 448 is cooled with anysuitable cooling fluid, such as air or water. In one exemplaryembodiment, air from the compressor 538 can be utilized as the coolingfluid.

The gas then can proceed through a line 452 to the adsorption zone 400that may include an adsorption vessel 410. The flue gas can pass throughthe vessel 410 and have a halogen-containing material, such aschlorides, adsorbed before exiting through a line 414 and a valve 418 tobe discharged to the atmosphere. Although the adsorption vessel 410 isdisclosed as a separate vessel with the line 424 between the vessels 410and 460, which can decrease the amount of gas that may backflow from theregeneration vessel 460 to the adsorption vessel 410, it should beunderstood that the adsorption vessel 410 can be incorporated into theregeneration vessel 460 by residing above the combustion zone 480. As anexample, the adsorption vessel 410 can be added to an existingregeneration vessel 460. In such an instance, integration can occur at aman-way present in the regeneration vessel 460. In both cases, theamount of gas that can flow from the regeneration vessel 460 to theadsorption vessel 410 may depend, in part, on the differential pressurebetween the regeneration vessel 460 and the adsorption vessel 410.Generally, the differential pressure can range from about 0.7-about 14kPa(g) (about 0.1-about 2 psig), preferably about 2 kPa(g) (about 0.3psig).

The flue gas exiting the combustion zone 480 can be at about 480-about540° C. (about 900-about 1000° F.). If the combustion zone 480 isoperating at low coking conditions, nitrogen can be added to thecombustion zone 480 to increase the flue gas stream flow to have, e.g.,sufficient gas flow for operating equipment. The flue gas that may enterthe adsorption vessel 410 is generally about 66-about 480° C. (about150-about 900° F.), preferably about 150-about 180° C. (about 300-about350° F.). Usually, the adsorption vessel 410 operates at a pressure ofabout 241 kPa(g) (about 35.0 psig). Generally, the adsorption conditionsare disclosed in U.S. Pat. No. 6,034,018 (Sechrist et al.). Typically,the total chloride removal in the flue gas stream is 99%, by mole, ofthe amount of chloride at the inlet. The chorine concentration in theflue gas stream can be reduced to about 1-about 10 mol-ppm and thehydrogen chloride concentration can be reduced to about 10-about 1000mol-ppm. If after adsorption the halogen-containing material is stillpresent at levels unacceptable for release to the atmosphere, anyconventional means, such as chloride scrubbers, can be utilized forremoving such material from the flue gas.

In another exemplary embodiment, the valve 438 can be closed and thevalve 488 can be opened to allow a slip stream from the discharge of therecycle compressor 484 instead of withdrawing gas from the regenerationvessel 460. Particularly, a portion of the recycle combustion gas can bewithdrawn through a line 492. Subsequently, the gas in the line 492 canpass through the cooler 448 and into the adsorption zone 400 through theline 452 for adsorbing halogen-containing material before exiting theadsorption zone 400, as described above.

Typically, the catalyst-disengaging zone 310 includes acatalyst-disengaging hopper 320, which can have the upper portion 324and lower portion 328, as discussed above. Although the upper and lowerportions 324 and 328 are depicted in the same vessel 320, it should beunderstood that each portion 324 and 328 can be contained in a separatevessel and communicate via a line. The pressure in the upper portion 324and the lower portion 328 can generally range from about 0-about 6900kPa(g) (about 0-about 1000 psig), preferably from about 30-about 620kPa(g) (about 5-about 90 psig), more preferably from about 240-about 410kPa(g) (about 35-about 60 psig), and optimally about 240-about 310kPa(g) (about 35-about 45 psig). Typically, the lower portion has apressure of about 243 kPa(g) (about 35.3 psig) and a pressure letdownpipe can be incorporated between the upper portion 324 and the lowerportion 328.

In one exemplary embodiment, a portion of the recycle gas, containinghydrogen, from the hydrocarbon conversion zone 210 can be utilized toelutriate the spent catalyst in the catalyst-disengaging hopper 320. Theelutriation gas can pass through a line 340 and be heated by anexchanger 344, using any suitable fluid, such as steam or anotherprocess stream, to a temperature, such as about 180° C. (about 350° F.),for the catalyst to adsorb material in the adsorption vessel 410.Typically, the temperature of the gas in the line 340 can be monitoredwith a thermocouple 350. Afterwards, the purified gas can enter a gasdeflector 338, and if desired, annular baffles 334 through a line 354 tomaintain the temperature of the catalyst for adsorption. In anotherexemplary embodiment if the disengaging hopper and regeneration vesselpressure exceeds the pressure of the hydrocarbon conversion zone, a netgas compressor can be utilized to supply gas to elutriate the spentcatalyst. The gas from the net gas compressor can have a similarcomposition as the net gas, but can have a destination to a highpressure hydrogen header or a fuel gas header absent utilizing at leasta portion to elutriate the spent catalyst.

The inert gas buffer 380 can be created between the gases from thehydrocarbon conversion zone 210 and the gases from the regeneration zone420 that pass through the adsorption zone 400. Particularly, the inertgas buffer 380 may be located below the gas inlet for elutriating andheating the spent catalyst and above the adsorption zone 400. The inertgas, such as nitrogen, typically is passed through a line 360 and heatedby a heat exchanger 364, with any suitable heat source, such as steam oranother process stream, provided through a line 368. Afterwards, thenitrogen may pass through a valve 372 to the lower portion 328 of thecatalyst-disengaging hopper 320. Typically, the inert gas buffer createsa volume at a slightly higher pressure of generally about 0.7-about 14kPa(g) (about 0.1-about 2 psig), preferably about 2 kPa(g) (about 0.3psig) than the surrounding regions to prevent intermingling of gasesfrom the upper portion 324 (that may contain hydrogen) and from theadsorption vessel 410 (that may contain oxygen). Excess gas, typicallyhaving a composition of hydrogen, hydrocarbon, and nitrogen, can escapethrough a line 374 at a pressure of about 241 kPa(g) (about 35.0 psig).Differential pressure sensors 378 and 384 can monitor the differentialpressure above and below the buffer 380 and control the introduction ofnitrogen by the valve 372. The differential pressure sensor-controller378 can measure the pressure difference between the zones 394 and 390 inthe lower portion 328, while the differential pressure sensor-controller384 may measure the pressure difference between the zone 390 and theadsorption vessel 410. Typically, the difference in pressure may bemeasured by each differential pressure sensor-controller 378 and 384 andis generally for each about 0.7-about 14 kPa(g) (about 0.1-about 2psig), preferably about 2 kPa(g) (about 0.3 psig). In addition, theexiting of gas from the adsorption vessel 410 can be controlled by adifferential pressure controller 456 monitoring the difference inpressures between the adsorption vessel 410 and near the entry point ofthe gases in the line 374. Typically the difference in pressure at thesetwo points is maintained at about 0 kPa (about 0 psi), i.e. usually bothpoints have a pressure of about 240 kPa(g) (about 35.0 psig). Thispressure is slightly lower than the pressure associated with the inertgas buffer 380, which typically has a slightly higher pressure along thepath of the catalyst flow. Generally, the catalyst-disengaging hopper320 can be operated up to a temperature of about 260° C. (about 500° F.)and the line 386 has sufficient length to maintain the inert gas buffer380 without excessive inert gas consumption.

In an alternative embodiment, although not depicted, the buffer 380 canbe provided between the catalyst disengaging zone 310 and the adsorptionzone 400, such as the line 386. In such an embodiment, the catalystdisengaging zone 310 can contain a single atmosphere having, e.g.,hydrogen and hydrocarbons.

As discussed above, the present regeneration unit can include anadsorption zone 400 which can be added to an existing pressurizedhydrocarbon conversion unit having a regeneration zone 420. Thus, thismodification can be made to an existing unit and allow the recovery andremoval of chlorides from a flue gas stream, that is optionallydischarged to the atmosphere. Consequently, the present invention canimprove the operations of existing units to meet environmentalstandards.

Without further elaboration, it is believed that one skilled in the artcan, using the preceding description, utilize the present invention toits fullest extent. The preceding preferred specific embodiments are,therefore, to be construed as merely illustrative, and not limitative ofthe remainder of the disclosure in any way whatsoever.

In the foregoing, all temperatures are set forth uncorrected in degreesCelsius and, all parts and percentages are by volume, unless otherwiseindicated.

From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. A regeneration unit for a hydrocarbon conversion catalyst for ahydrocarbon conversion zone, comprising: (a) a catalyst-disengaginghopper having an upper portion and a lower portion receiving spentcatalyst from the hydrocarbon conversion zone; (b) an adsorption vesselcommunicating with the catalyst-disengaging hopper adapted to receive aninert gas at least between the upper portion of the catalyst-disengaginghopper and the adsorption vessel; and (c) a regeneration vesselcomprising a combustion zone wherein a conduit extends into theregeneration vessel and communicates the combustion zone with theadsorption vessel for passing a flue gas to the adsorption vessel.
 2. Aregeneration unit according to claim 1, further comprising a coolerwherein the flue gas exiting the combustion zone through the conduit ispassed through the cooler before entering the adsorption vessel.
 3. Aregeneration unit according to claim 1, wherein the inert gas comprisesnitrogen.
 4. A refinery or a petrochemical production facilitycomprising the regeneration unit according to claim 1.